System for controlling a strip material roll as a function of speed or tension of traveling strip material



y 1970 w. c CARTER u 3,519,903

SYSTEM FOR CONTROLLING A STRIP MATERIAL ROLL AS A FUNCTION OF SPEED OR TENSION OF TRAVELING STRIP MATERIAL Filed Sept. 5, 1967 2 Sheets-Sheet l SYSTEM FOR CONTROLLING A STRIPv MATERIAL ROLL AS A FUNCTION July 7, 1970 w. c. CARTER u OF SPEED OR TENSION OF TRAVELING STRIP MATERIAL Filed Sept. 5, 1967 2 Sheets-Sheet 23 motoxw 04ml mOkOE IMCSIJ .rzwmmDo mm: 3: .rzmmmno United States Patent 3,519,903 SYSTEM FOR CONTROLLING A STRIP MATERIAL ROLL AS A FUNCTION OF SPEED OR TENSION OF TRAVELING STRIP MATERIAL Woodward C. Carter II, West Seneca, N.Y., assignor to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Sept. 5, 1967, Ser. No. 665,568 Int. Cl. H02p /00 US. Cl. 318-6 14 Claims ABSTRACT OF THE DISCLOSURE An electrical control system for strip material winding and/or unwinding apparatus wherein the surface speed of a strip material roll, either employ or loaded, is first matched to the lineal speed of traveling strip material, followed by a smooth transition from speed control of the roll to control based on the tension in the strip material being wound or unwound.

BACKGROUND OF THE INVENTION While not limited thereto, the present invention is particularly adapted for use with flying splicers utilized in the paper and man made fiber industries. Such splicers are used to couple traveling strip material to a roll in both winding and unwinding systems; and since these products may easily be excessively stretched or tom, the main control for the winding or unwinding strip material roll is responsive to a direct measurement of the tension in the strip. The term strip material roll as used herein includes both windup and unwind rolls, and covers empty rolls as well as partially or fully loaded rolls. Thus the term strip material roll may refer to an empty roll (devoid of strip material) which is about to be loaded with strip, as well as to a roll of strip material, being wound, or unwound, or about to be unwound. In unwinding apparatus, for instance, strip whose tension is being controlled and which is issuing from an almost empty roll must be severed while the forward end of a new full roll is spliced onto the trailing end of the severed strip, all of this occurring at full production speed without loss of tension in the strip or over tensioning of the strip. Similarly, in winding apparatus, when one roll is filled, the strip must be automatically threaded onto a new core (empty roll) and severed from the filled roll, again at full production speed and without loss of tension control in the strip.

A drive system for a flying splicer must have three important features. First, the new roll, empty in a winding operation and full in an unwinding operation, must be surface speed matched to the lineal speed of the strip being wound or unwound. Secondly, at the instant of splicing, the new roll must change bumplessly from speed regulation to tension regulation. Otherwise, the paper or other material may tear due to transient conditions. The outgoing roll, of course, is stopped after it is taken off tension regulation. Thirdly, after the splice is made, the drive system for the new roll must accurately control tension over the speed range and roll diameter range. Performing these three functions over a wide range of roll diameters is very difficult because of widely varying inertia characteristics of the driven roll and sometimes because of the inability to directly sense roll surface speed prior to a splice.

In the past, these functions were performed by a system wherein a speed servo loop was inside a tension servo loop to facilitate a bumpless transition from speed to tension regulation. That is, the feedback signal from the speed loop was simply added to the tension servo loop. This ice requires that the tension loop response be slower than the speed loop. In practice, then, the response of the tension loop must be quite slow since the speed loop must be slowed down sufliciently itself to accommodate the wide variations in roll intertia over the range of diameters of the various rolls of strip material. The response speed of the tension loop is then just barely acceptable.

Furthermore, it is very difficult to build a roll diameter detector system that is not subject to some jerkiness in following the :builddown or buildup of roll diameter, or that does not exhibit some transient in moving from its preset point before a splice to its initial detecting point after a splice. These roll diameter detector characteristics introduce transients directly into the speed loop inside the tension loop, and the resulting tension disturbance can be excessive before the tension loop has a chance to correct for it.

SUMMARY OF THE INVENTION As an overall object, the present invention seeks to provide a new and improved control system for flying splicer drives which overcomes the aforementioned and other disadvantages of prior art systems, particularly those wherein a speed servo loop was inside the tension servo loop.

Another object of the invention is to provide a control system for fiying splicer drives which employs both a speed servo loop as well as a tension servo loop, the two loops being operated in the parallel mode with only one active at any given time, the other being switched off by a biased diode. As will be seen, this eliminates the difficulty involved in attempting to match the speed and ten sion loops and avoids tension disturbances in the tension loop immediately following a splice.

In accordance with the invention, there is provided, in a system for controlling a drive motor for a strip material roll, means for producing a first electrical signal proportional to the speed of traveling strip material about to be coupled to the roll for windup or unwinding, means for producing a second electrical signal proportional to the tension in the strip material, motor control apparatus for the drive motor, a first servo loop for applying the first electrical signal to the motor control apparatus, a second servo loop in parallel with the first loop for applying the second electrical signal to the motor control apparatus, and means for selectively connecting one of said servo loops to the motor control apparatus while disconnecting the other and vice versa. The paralleled first and second (speed and tension) loops may or may not drive inner loops such as current or voltage loops roviding auxiliary functions such as torque limit.

With this arrangement, the drive motor is controlled by either a speed loop or a tension loop, the two loops being operated in the parallel mode with only one active at any given time, the other being switched off, preferably by a biased diode. In an unwinding operation, the unwind is started with speed regulation while the surface or circumferential speed of the roll (either directly measured or calculated from r.p.m. and diameter) is matched to the lineal speed of the strip material. At the proper instant during a splice, the tension loop is switched on and the speed loop is switched off. The tension loop then controls the unwind until it is stopped after the next splice is made, or until it is intentionally turned olf.

In a winding operation, the windup is again started under speed regulation with the rotational speed of a core of known diameter adjusted such that its surface or circumferential speed matches that of the strip material. During the splice (transfer of the strip from the full to the empty core), the speed loop is switched out of the system and the tension loop, in turn, connected to the 3 motor control; whereupon the winding operation progresses under tension control.

The above and other objects and features of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings which form a part of this specification, and in which:

FIGS. lA-lE schematically illustrate the operation of a flying splicer for an unwinding operation;

FIGS. 2A-2F schematically illustrate the operation of a flying splicer for a winding operation; and

FIG. 3 is a schematic circuit illustration of one embodiment of the present invention. A set of equipment as shown in FIG. 3 is required for each driven spindle (A, B, A and B) in FIGS. 1 and 2, except that devices 72, 76, 78 and 156 may be common.

With reference now to the drawings, and particularly to FIGS. lA-lE, the unwind mechanism shown includes a rotatable assembly having four arms identified as A, B, C and D spaced 90 apart from each other. The arms A and B carry cores 12 and 14 on which rolls of paper or the like to be unwound are loaded, one of said rolls being identified in FIG. 1A by the reference numeral 16. The other two arms C and and D carry idler ro ls 18 and 20 at their extremities. The strip material issuing from the roll 16 passes around roll 22, thence over a force transducer 24, and finally around roll 26. Beneath the roll 16 is a flying cut off mechanism comprising an arm 28 rotatable about an axis 29 and having a shear 30 at its opposite end. Between the axis 29 and shear 30 is a roll 32 which, as will be seen, serves to splice the forward end of a new roll of paper to be unwound to the trailing end of strip material from a roll which has almost been expended.

In the position shown in FIG. 1A, a splice has just been made and the roll 16 proceeds to unwind. In FIG. 1B, a a new full roll 17 has been loaded onto the core 14 of arm B while the roll 16 reduces in diameter. In FIG. 1C, the turret has rotated in the direction of arrow 34 through 180, thereby positioning arm A and roll 16 to the right while positioning the new roll 17 above the shear 30 and roll 32. Note that under these circumstances, the strip issuing from roll 16 passes over roll 18 on the arm C.

In FIG. 1D, the arm 28 is rotated upwardly whereby the shear severs the strip issuing from roll 16, which is now almost completely spent. At the same time, the roll 32 presses the trailing end of the strip from roll 16 into engagement with the leading edge of the strip on roll 17, which leading edge is preglued. However, before the splicing operation begins, the roll 17 on core 14 must be rotated such that its surface or circumferential speed matches the lineal speed of the traveling strip. This may be accomplished, for example, by means of a tachometer 36 in engagement with the periphery of the roll 17 and by comparing the output of this tachometer with the output of a tachometer on the traveling strip material. As will be understood, the movement of the arm 28 must be synchronized with the arrival of the pre-glued forward end of the strip on roll 17; however this synchronization apparatus forms no part of the present invention. In FIG. 1B, the cycle just described is again repeated; but in .this case the positions of arms A and B are reversed with respect to the showing in FIG. 1A.

In FIGS. 2A-2F, a winding operation is illustrated. The apparatus again includes a rotatable member 38 having four arms A, B, C and D thereon, the arms A and B are provided with cores 40 and 42; while the arms C and D are provided with idler rolls 44 and 46. In the illustration given in FIG. 2A, the entering strip material 48 passes over a force transducer 50 and around a movable roll 52, thence to the core 42 which has been rotated to a surface speed matching the lineal speed of the strip 48.

In the illustration shown in FIG. 2A, the winding operation has just begun. In FIG. 2B, the assembly 38 is rotated in the direction of arrow 54 while winding of the strip material on core 42 progresses. In FIG. 20, the previously wound roll 56 on core 40 has been removed and core 40 effectively becomes a new empty strip material roll ready to accept strip material as in FIGS. 2E and 2F; and in FIG. 2D, the assembly 38 is further rotated in the direction of arrow 54 until the arm B carrying core 42 and newly-wound roll 58 is at the top of the assembly. Under these conditions, the strip passes around idler roll 46 on arm D. In FIG. 2E, the assembly 38 has been further rotated in the direction of arrow 54 such that the core 40 (empty roll) is now in the path of the strip material 48, and the surface speed of the empty roll 40 is matched to the lineal speed of the entering strip 48. After this occurs, the roll 52 is moved along the direction of arrow 60 to the dotted line position shown such that the strip material 48 must pass almost completely around the core 40. Finally, in FIG. 2F, arm 62 is actuated to move roll 64 into engagement with the core 40 while simultaneously severing the strip being fed to roll B by means of shear 66. At this point, the cycle is again repeated.

Since the core 14 in FIG. 1A is devoid of strip material it may be referred to as an empty strip material roll. The same is true of core 12 in FIG. 1B, and core 40 in FIGS. 2C and 2D. Rolls 16 and 17 of strip material in FIGS. 1B and 1C may be referred to as loaded strip material rolls, because they have strip material in them. Roll 17 in FIGS. 1B and 1C is a fully loaded strip material roll. The above statements in this paragraph are included to illustrate examples of the use of the term strip material roll, which as hereinbefore indicated encompasses an empty roll (core) upon which strip material is to be wound as well as the composite of core partially or fully loaded with strip material.

Before a splice is made to couple the traveling strip to a new strip material roll, either in a winding or unwinding operation, the surface speed of the incoming ro l must be matched to the lineal speed of the traveling strip material. However, once a splice is made, the speed of the roll being wound or unwound must be controlled as a function of the tension in the strip material. Furthermore, as was mentioned above, this transition from speed control to tension control must occur as smoothly as possible and without any transient effects since otherwise the paper or other strip material may tear or go loose.

The apparatus of the present invention for transferring from speed control to tension control or vice versa is shown in FIG. 3. A tension signal on lead 70 is derived from a force transducer 72 over which the strip material passes; while a line speed reference signal on lead 74 is derived from a tachometer generator 76 connected to pinch rolls 78 through which the incoming or outgoing strip material 80 passes. The core 82 carrying a roll of paper 84 is driven through mechanical linkage 86 by means of a drive motor 88. As shown, the motor 88 is driven in a Ward-Leonard arrangement by means of a generator 90 having a field winding 92 connected to a power amplifier 94. A static armature supply such as a thyristor armature supply could also be used. Motor 88 is also provided with a field winding 97 connected to a motor field excitation circuit 99. The field produced by winding 97 may be varied as the diameter and inertia of the strip material roll 84 change, or it may remain fixed at some value and the power ratings of the armature loop chosen accordingly.

Connected to the input of the power amplifier 94 is an o erational amplifier 96 used as a current regulator and aving a feedback path including a resistor 98 and capacitor 100. To the input of the operational amplifier 96 is applied the output of a tension regulator, enclosed by broken lines and identified by the reference numeral 102. Alternatively, the amplifier 96 is driven by the output of a speed regulator, also enclosed by broken lines and identified by the reference numeral 104. Negative feedback proportional to armature current and derived from resistor 105 is applied to the input of amplifier 16 through a path including isolating amplifier 106 and resistor 108.

In order to detect the instantaneous diameter of the strip material roll 84, a roll diameter detector is provided including an operational amplifier 110 having a feedback path including resistor 112 and capacitor 114. The inputs to the operational amplifier 110 include an actual lineal surface speed signal on lead 116, a calculated surface speed signal on lead 118 and a small alternating current signal of about 1 cycle per second frequency from source 120. The output of the amplifier 110, in turn, is used to drive a servomotor 122.

The system is in equilibrium only if the net input to the roll diameter detector amplifier 110 is zero, since the amplifier and servomotor 122 have an integrating characteristic which requires zero input for a constant position of the motor 122. Neglecting the small magnitude alternating current input from source 120, the amplifier input is made equal to the difference between a voltage proportional to the surface speed from tachometer 76 and a voltage proportional to the product of revolutions per minute of the roll 84 and the shaft position of motor 122. In this respect, a tachometer generator 124 is connected to the core 82; and the output of the tachometer generator 124, being a signal proportional to revolutions per minute, is applied across the resistor 126 as a voltage dividing potentiometer. The resistor 126, in turn, is provided with a movable tap connected to the servomotor 122 such that the voltage on the tap 128 and, hence, lead 118 will be proportional to the product of the output voltage of tachometer generator 124- and the shaft position of servomotor 122. If the position of the shaft of servomotor 122 was proportional to diameter, the arrangement would multiply revolutions per minute times diameter, thereby producing a signal proportional to instantaneous surface speed on the lead 118. Since the servomotor 122 is operated by amplifier 110 whenever the difference between the signals on leads 116 and 118 is significantly different from zero (to return it to essentially zero), the shaft rotation of the servomotor 122 is kept proportional to diameter and the voltage on the tap 128 proportional to calculated roll surface speed.

'In actual practice, the roll diameter changes at a very slow rate. To aid the servomotor 122 in moving at such slow rates smoothly and without jerking, the small alternating current signal of about 1 cycle per second frequency from source 120 is superimposed on the input signals on leads 116 and 118. This low frequency signal is small enough and rapid enough to have no effect on roll diameter determining capabilities. Its effect is to act as a dither oscillation to keep the servomotor 122 broken away from its static friction load, ready and able to move slowly and smoothly as required.

As will be understood, when the roll on core 82 1S changed, the roll diameter detector must be reset to the new diameter. This can be accomplished by a servo fol- .lower reset circuit, not shown, which causes the position of the shaft of servomotor 122 to follow a pot reset by an operator. The position of the shaft of servomotor 122 will then be correct for the new roll. However, if the system requirements are such that the roll diameter detector setting need not be correct initially, the detector will reset itself during the first few seconds of operation. In usual practice, the windup roll diameter detector is preset to the empty core diameter by a limit switch contact. On the other hand, the unwind roll diameter detector can be allowed to reset itself during the time the unwind is being surface speed matched via a surface mounted tachometer, not shown, to the machine surface speed prior to a splice. This surface mounted tachometer would correspond, for example, to that identified by the reference sponding to tachometer 36 in FIGS. 1C'lE.

The speed controller 104 includes an operational amplifier 130 having a feedback path including a current limiting limiter 132. Applied to the input of amplifier 130 via resistor 134 is a speed reference signal from tachometer generator 76 on lead 74. Also applied as negative feedback to the input of amplifier 130 via resistor 136, and with switch 138 in the position shown, is the calculated surface speed signal on lead 118. As will be understood, this calculated surface speed signal, in the case of an unwind mechanism, can be replaced by an actual surface speed signal derived from a tachometer corresponding to tachometer 36 in FIGS. 1'C1E.

On the other hand, during a windup operation, and since the diameter of a new core (new empty roll) is fixed, the positions of the contacts on switch 138 can be reversed so that a signal from tachometer generator 124 is applied to the input of amplifier 130 rather than a calculated or actual surface speed si-gnal. That is, since the diameter of the core (empty roll) is fixed, a signal proportional to revolutions per minute is also proportional to surface or circumferential speed.

Finally, and assuming that the relay coil 140 is energized to close contacts 142, a high positive voltage will be applied to the input of operational amplifier 130 via resistor 144. When this high positive input is applied to the amplifier 130, it saturates, thereby effectively disconnesting the speed regulator 104 from the control for generator 90 and motor 88 in a manner hereinafter described. The relay 140, in turn, will be energized by means of closure of contacts 146 whenever the system switches from spee -ontrol to tension control.

The tension control circuit 102 likewise includes an operational amplifier 148 having a feedback path including a current limiting limiter 150. Applied to the input of amplifier 148 via resistor 154 is a desired tension signal derived from a reference source 156, of one polarity for windup and opposite polarity for unwind. Applied as negative feedback to the input of amplifier 148 via resistor 152 is the tension signal from transducer 72 on lead 70. As will be understood, the tension in the strip can be varied by the operator in moving the tap on potentiometer 156; and this comprises the main overall control for the system. Finally, a high positive voltage can be applied to the input of amplifier 148 via resistor 158 to saturate the amplifier and disconnect it from the control for motor 88 when relay 140 is deenergized. As will be seen, when the relay 140 is deenergized, the system is under speed control. At all other times, the relay 140 will be energized to connect the tension control to power amplifier 94.

The output of operational amplifier 130 is connected to a common lead 158 through a diode 160. Similarly, the output of amplifier 148 is connected through diode 162 to the lead 158. Operational amplifier 130 is provided with a feedback path including lead 158, potentiometer 164, potentiometer 166, capacitor 168 and resistor 170. Similarly, the operational amplifier 148 in the tension controller is provided with a feedback path including lead 158, potentiozmeters 164 and 172, capacitor 174 and resistor 176. The potentiometer 164 is included in a voltage divider network including resistors 178 and 180*, the junction of resistors 178 and 164 being connected to the lead 158 and, through resistor 182, to the input of operational amplifier 96.

As an illustration of the operation of the diodes .and 162, assume that the voltage between the anode of diode 160 and ground is V and that the voltage between the anode of diode 162 and ground is V Furthermore, assume that the voltage between the junctions of resistors 178 and 164 and ground is V the output voltage. If there are no signals on the anodes of diodes 160' and 162 (V and V 0), the voltage at the input to operational amplifier 96 will be determined by the voltage divider network comprising resistors 178, 164, and 180. Assuming that the resistors in the voltage divider network are chosen such that the quiescent (i.e., no input) value of V is volts and that V and V operate over a :9.5 volt range, the quiescent value of V is such that V or V always has the range required to forward bias its particular diode in the absence of any signal from other inputs. Stated in other words, the voltage divider network insures that a net negative voltage will always exist on the cathode of either diode 160 or 162.

If the output of amplifier 130 is more positive than amplifier 148, for example, the only equilibrium condition which can exist is with diode 160 biased on and diode 162 biased off. The output voltage V supplied to amplifier 96 is, therefore, equal to V In general, the circuit will automatically cause V to follow the more positive input, switching off the other less positive (more negative) input. Due to the l0 volt quiescent value of V the last statement holds for input voltages in the $9.5 volt range: and if both inputs are negative, V will follow the least negative (more positive) one.

The diode switch comprising elements 160 and 162 can be operated by forcing the input, which is to be switched off, to negative saturation, inherently forcing the other input to be more positive and, therefore, to be switched on. This is the function of relay coil 140 and contacts 142. That is, when coil 140 is deenergized, amplifier 148 is forced into negative saturation and diode 162 cuts off. On the other hand, when coil 140 is energized, contacts 142 close, amplifier 130 is forced into negative saturation, and diode 160 is cut off. It will be noted that as the diameter of the roll changes and the shaft position of the servomotor 122 changes, the position of the movable tap on potentiometer 164 also changes. Thus, the speed and tension 100p gains are adjusted by the roll diameter detector as a function of roll diameter. This effectively eliminates varying roll diameter and inertia as a factor in the drive dynamics and permits an optimum speed and tension loop response at all diameters.

With the arrangement shown, the speed and tension loops operate in parallel, being at all times preconditioned to the proper output to avoid a transient if either is switched in and the other out by one of the diode switches 160 or 162. If it is assumed that a splice in an unwinding operation is occurring and that the drive being discussed is the incoming full roll drive, contacts 146 will be open and the contacts of switch 138 will be in the position shown with calculated surface speed being fed back to the input of amplifier 130 along with the desired (reference) surface speed from tachometer 76. The roll diameter detector is assumed to have been previously preset to the incoming roll diameter. Alternatively, a tachometer, such as tachometer 36 shown in FIGS. 1C-1E, can be employed to produce an actual surface speed feedback signal from the roll 84. (As the unwinding operation has progressed through FIGS. lA-lC, an identical system driving the unwinding roll will have been under tension control; and its contacts 146 will have been closed to energize relay 140 and close contacts 142, thereby saturating amplifier 130.) When the arm 28 is actuated as in FIG ID, a limit switch on the arm 28 will close contacts 146 on the incoming roll drive, thereby closing contacts 142 and saturating the speed operational amplifier 130. Under these circumstances, the incoming roll drive tension 100p takes over; and since the initial voltage on the tension loop feedback capacitor 174 has been kept proportional to the voltage on the speed loop feedback capacitor 168, the proper output voltage (V information required for a smooth transition is already stored in the tension loop and the transition occurs without any jerkiness.

In the case of a winding operation as shown in FIGS. 2A2F, the starting diameter of the core 42 (starts as empty strip material roll) is fixed. Consequently, the positions of the contacts on switch 138 are reversed such that a signal proportional to revolutions per minute is fed back to the input of amplifier 130 along with the reference speed signal on lead 74. That is, since the diameter of the incoming core (empty strip material roll) is constant, a signal proportional to revolutions per minute is also proportional to surface speed.

In FIGS. 2A-2E, the system driving the winding roll B is under tension control with its relay coil 140 energized. During a splice sequence as shown in FIGS. 2E and 2F, the system driving the incoming empty strip material roll (core 44)) is started under speed control with its relay 140 deenergized. Transfer of tension control from B to A during the condition depicted by FIG. 2F is made by changing the state of the systems 146 contacts in a manner similar to that depicted for the unwinding, again with a very smooth transition. Even though the feedback to the amplifier 130 is from tachometer 124, the roll diameter detector amplifier and servomotor 122 are still effective to change the gain of the loops via potentiometer 164 as the diameter of the roll increases during a winding operation.

Although the invention has been shown in connectlon with certain specific embodiments, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of the invention. Such changes include, but are not limited to, the following:

(1) Use of a static armature supply instead of an M-G set supply.

(2) Use of swing roll position feedback as a tension signal instead of a force transducer output.

(3) Use of either a fixed motor field or a motor field adjusted as some function of diameter.

(4) Use of another type of multiplier for the gain changing and roll diameter detecting function.

(5) Use of other than P+I controllers.

(6) Use of inner loops other than a current loop.

(7) Addition of programmed tension setpoints such as taper tension.

(8) Use of a calculated tension feedback (say some function of motor current) instead of a directly measured tension feedback.

(9) Use of -a digital or relay operated roll diameter detector instead of the continuous type depicted here.

(10) Utilization of roll diameter information from an arm or similar device directly determining it instead of computing it.

(11) USe of the paralleled speed loop as a device to match spindle r.p.m. to another spindle r.p.m. prior to changing an unwinding roll from being driven from one drive to a second drive while maintaining tension control of the sheet unwinding from the roll at all times. Such a function is required on the so-called transfer type flying faster unwinds.

(12) Although amplifiers 96, 110, and 148 are shown by way of example as P+l (proportional plus integral) controllers other suitable types may be employed, for example P+I+D (proportional plus integral plus derivative) controllers. More detailed examples of P-l-I and P+I+D controllers are shown in US. Pat. No. 3,324,363. This patent also shows other techniques including an example of a current regulating loop which may be employed in the system disclosed herein.

I claim as my invention:

1. In apparatus for handling traveling strip material wherein there is a strip material roll for association with the traveling strip material, a drive system for controlling the rotation of the said strip material roll as a function of either the speed of the strip material or of the ten sion of the strip material, said drive system comprising:

(A) a motor for driving said roll;

(B) motor control apparatus for said motor;

(C) means for producing a first electrical signal proportional to the speed of the strip material;

(D) means for producing a second electrical signal proportional to the tension in the strip material;

(E) a first servo loop responsive to said first signal for controlling said motor as a function of the speed of the strip material, said loop including a first operational amplifier;

(F) a second servo loop in parallel with the first loop and responsive to said second signal for controlling said motor as a function of the tension in the strip material, said second loop including a second operational amplifier;

(G) and means for selectively connecting one of said servo loops to the motor control apparatus while the other is disconnected, and vice versa, said means comprising (1) a voltage divider network,

(II) first and second unidirectional devices each connecting the output of a different one of said amplifiers to a point on said voltage divider network, whereby in response to polarity difference between the respective outputs of the amplifiers one of said unidirectional devices will conduct while the other blocks, or vice versa, depending on the direction of polarity difference, and

(III) means for selectively saturating either one of said amplifiers whereby the unidirectional device at the output of the saturated amplifier will be cut off while the unidirectional device at the output of the other amplifier will connect that amplifier to said point on the voltage divider network.

2. The apparatus of claim 1 wherein said first electrical signal is produced by a tachometer generator connected to pinch rolls through which the strip material passes and wherein said first electrical signal is compared with a third electrical signal in said first servo loop, the third electrical signal having a magnitude proportional to the circumferential surface speed of said roll of strip material, means for generating a fourth electrical signal which is proportional to desired tension in said strip material, and means in said second servo loop for comparing said second and fourth electrical signals.

3. The apparatus of claim 1 wherein said point on the voltage divider network is connected to the input of said motor control apparatus.

4. The apparatus of claim 2 including a tachometer generator operatively connected to said drive motor and adapted to produce an output signal proportional to revolutions of the roll per unit of time, a device for producing an electrical signal proportional to the diameter of said roll, and means responsive to the output of said tachometer generator and said electrical signal proportional to roll diameter for producing said third electrical signal proportional to circumferential surface speed of the roll.

5. The apparatus of claim 4 wherein the means for producing said third electrical signal comprises a servomotor device connected to said device for producing an electrical signal proportional to roll diameter and arranged to produce mechanical movement proportional to roll diameter, a potentiometer having a resistive element and a tap movable along the resistive element, means connecting said tap to the servomotor device whereby the position of the tap on the resistive element will be a function of roll diameter, and means for applying the output of said tachometer generator across said resistive element to produce said third electrical signal between said tap and one end of said resistive element.

6. The apparatus of claim 5 wherein the device for producing an electrical signal proportional to roll diameter comprises an operational amplifier having applied to its input said first electrical signal proportional to the speed of said strip material and the signal on the tap of said potentiometer.

7. The apparatus of claim 1 wherein the operational amplifiers are provided with feedback loops both including a potentiometer which forms part of said voltage divider network, and means for varying the position of the tap on said potentiometer as a function of roll diameter to thereby vary the gain of the said first and second servo loops as a function of roll diameter.

8. The apparatus of claim 1 wherein the drive motor is powered by an adjustable voltage source, and means for controlling said source in response to signals at the outputs of said operational amplifiers.

9. In apparatus for controlling rotation of a strip material roll in relation to traveling strip material, the combination comprising:

(A) a motor for driving said roll;

(B) motor control means for controlling said motor;

(C) means for producing a first signal representing desired reference speed;

(D) means responsive to said motor for producing a second signal that is a function of the speed of the motor;

(E) means for producing a third signal representing desired tension;

(F) means responsive to said traveling strip material for producing a fourth signal that is a function of the tension of the strip material;

(G) a speed controller that has an output circuit and produces an output signal in response to said first and second signals;

(H) a tension controller that has an output circuit and produces an output signal in response to said third and fourth signals;

(1) switching means having respective first and second inputs, and also having an output circuit coupled to said motor control means whereby said motor control means responds in accordance with signals appearing at said switching output circuit, said switching means being constructed to provide at its output circuit a control signal that is a function of that one of respective signals applied concurrently to the respective inputs of the switching means which is more of a particular polarity than the other; and

(J) means for coupling the output circuit of each of said speed and tension controllers to a different one of said first and second inputs of the switching means.

10. The combination as in claim 9 wherein there is means for selectively saturating any one of said controllers in a direction opposite to said particular polarity, whereby the output of only the unsaturated controller is passed by the switching means to said motor control means.

11. The combination as in claim 9 wherein there is means for detecting the diameter of said roll, and means responsive to the roll diameter detection means for controlling the respective gains of said speed and tension controllers as a function of roll diameter.

12. The combination as in claim 9 wherein said reference speed is the speed of the traveling strip material, and wherein said second signal is proportional to the peripheral speed of said strip material roll.

13. The combination as in claim 9 wherein each of said controllers comprises an operational amplifier, and wherein said switching means comprises first and second unidirectional devices, one connecting the output of one of the amplifiers to the switching means output circuit, the other connecting the output of the other amplifier to said switching means output circuit, said unidirectional devices being poled alike relative to the switching means output circuit, said amplifiers and switching means being arranged to operate in a mode wherein there will always be forward biased at least one of said unidirectional devices, and wherein there is means for selectively saturating any one of said operational amplifiers in a direction opposite to said particular polarity whereby the unidirectional device at the output of the saturated amplifier will be cut off while the unidirectional device at the output of the other amplifier will conduct to pass the Output of that amplifier to the switching means output circuit.

14. The combination of claim 13 wherein said switching means includes a junction in its output circuit to which like electrodes of said unidirectional devices are connected, a resistor having one end connected to said junction, and a voltage source connected to the other end of the resistor to insure that at all times at least one of the unidirectional devices will be conducting.

References Cited UNITED STATES PATENTS Peeples 3186 Asseo 3187 Hill 3186 Carter 3 186 Hill 3 18-6 Bentley 318-6 10 0111s L. RADER, Primary Examiner A. G. COLLINS, Assistant Examiner 

